Relay device, relay method, and optical communication system which uses relay device

A relay device comprising:

• a first transmitting and receiving unit that performs transmission and reception of optical signals to/from a first PON line on an upper-level side, and mutual conversion between the optical signals and electrical signals;
• a second transmitting and receiving unit that performs transmission and reception of optical signals to/from a second PON line on a lower-level side, and mutual conversion between the optical signals and electrical signals;
• a relay processing unit that relays a downstream frame received by the first transmitting and receiving unit to the second transmitting and receiving unit, and relays an upstream frame received by the second transmitting and receiving unit to the first transmitting and receiving unit;
• and
• a control unit that follows upstream multiple access control performed by a station side device, for transmission of the upstream frame to be transmitted by the first transmitting and receiving unit to the station side device, and independently performs upstream multiple access control for reception of the upstream frame received by the second transmitting and receiving unit from a home side device, wherein
• the first transmitting and receiving unit can receive a downstream optical signal at a higher transmission rate than that of the second transmitting and receiving unit, and the relay processing unit has a downstream buffer for absorbing a difference in downstream transmission rate between the two transmitting and receiving units.

A relay device comprising:

• a first transmitting and receiving unit that performs transmission and reception of optical signals to/from a first PON line on an upper-level side, and mutual conversion between the optical signals and electrical signals;
• a second transmitting and receiving unit that performs transmission and reception of optical signals to/from a second PON line on a lower-level side, and mutual conversion between the optical signals and electrical signals;
• a relay processing unit that relays a downstream frame received by the first transmitting and receiving unit to the second transmitting and receiving unit, and buffers an upstream frame received by the second transmitting and receiving unit and relays the upstream frame to the first transmitting and receiving unit;
• and
• a control unit that follows upstream multiple access control performed by a station side device, for transmission of the upstream frame for a case of transmitting, by the first transmitting and receiving unit, the buffered upstream frame to the station side device, and independently performs upstream multiple access control for reception of the upstream frame for a case of buffering at least one frame received by the second transmitting and receiving unit from a home side device.